1. Related Art
Rapid Prototyping and Manufacturing (RP&M) is the name given to a field of technologies that can be used to form three-dimensional objects rapidly and automatically from three-dimensional computer data representing the objects. RP&M can be considered to include three classes of technologies: (1) Stereolithography, (2) Selective Deposition Modeling, and (3) Laminated Object Manufacturing.
The stereolithography class of technologies create three-dimensional objects based on the successive formation of layers of a fluid-like material adjacent to previously formed layers of material and the selective solidification of those layers according to cross-sectional data representing successive slices of the three-dimensional object in order to form and adhere laminae (i.e. solidified layers). One specific stereolithography technology is known simply as stereolithography and uses a liquid material that is selectively solidified by exposing it to prescribed stimulation. The liquid material is typically a photopolymer and the prescribed stimulation is typically visible or ultraviolet electromagnetic radiation. The radiation is typically produced by a laser though other sources of radiation are possible such as arc lamps, resistive lamps, and the like. Exposure may occur by scanning a beam or by controlling a flood exposure by use of a light valve that selectively transmits or reflects the radiation. Liquid-based stereolithography is disclosed in various patents, applications, and publications of which a number are briefly described in the Related Applications section hereafter.
Another stereolithography technology is known as Selective Laser Sintering (SLS). SLS is based on the selective solidification of layers of a powdered material by exposing the layers to infrared electromagnetic radiation to sinter or fuse the powder particles. SLS is described in U.S. Pat. No. 4,863,538, issued Sep. 5, 1989, to Deckard. A third technology is known as Three Dimensional Printing (3DP). 3DP is based on the selective solidification of layers of a powdered material which are solidified by the selective deposition of a binder thereon. 3DP is described in U.S. Pat. No. 5,204,055, issued Apr. 20, 1993, to Sachs.
The present invention is primarily directed to stereolithography using liquid-based building materials (i.e. medium). It is believed, however, that the techniques of the present invention may have application in the other stereolithography technologies.
Selective Deposition Modeling, SDM, involves the build-up of three-dimensional objects by selectively depositing solidifiable material on a lamina-by-lamina basis according to cross-sectional data representing slices of the three-dimensional object. The material being dispensed may be solidified upon cooling, by heating, exposing to radiation, or upon application of a second physical material. A single material may be dispensed or multiple materials dispensed with each having different properties. One such technique is called Fused Deposition Modeling, FDM, and involves the extrusion of streams of heated, flowable material which solidify as they are dispensed onto the previously formed laminae of the object. FDM is described in U.S. Pat. No. 5,121,329, issued Jun. 9, 1992, to Crump. Another technique is called Ballistic Particle Manufacturing, BPM, which uses a 5-axis, ink-jet dispenser to direct particles of a material onto previously solidified layers of the object. BPM is described in PCT publication numbers WO 96-12607, published May 2, 1996, by Brown; WO 96-12608, published May 2, 1996, by Brown; WO 96-12609, published May 2, 1996, by Menhennett; and WO 96-12610, published May 2, 1996, by Menhennett. A third technique is called Multijet Modeling, MJM, and involves the selective deposition of droplets of material from multiple ink jet orifices to speed the building process. MJM is described in U.S. Pat. No. 5,943,235 to Earl et al., and U.S. patent application Ser. No. 08/722,335, filed Sep. 27, 1996, by Leyden et al. (both assigned to 3D Systems, Inc. as is the instant application).
Laminated Object Manufacturing, LOM, techniques involve the formation of three-dimensional objects by the stacking, adhering, and selective cutting of sheets of material, in a selected order, according to the cross-sectional data representing the three-dimensional object to be formed. LOM is described in U.S. Pat. Nos. 4,752,352, issued Jun. 21, 1988, to Feygin, 5,015,312, issued May 14, 1991, to Kinzie, and 5,192,559, issued Mar. 9, 1993, to Hull et al.; and in PCT Publication No. WO 95-18009, published Jul. 6, 1995, by Morita.
Though, as noted above, the techniques of the instant invention are directed primarily to liquid-based stereolithography object formation, it is believed that some of the techniques may have application in the LOM and/or SDM technologies where application of a beam or other laminae forming element must be precisely controlled.
Needs exist in the stereolithographic arts for improved beam generation techniques and positioning techniques. A first need exists for enhanced effective life of solid state ultraviolet producing lasers in a stereolithographic system. A second need exists for maintaining substantially uniform exposure over the length of each vector while simultaneously scanning as fast as possible, maintaining adequate positional control and minimizing the overall exposure time. A third need exists for improved control of the laser power that is produced and applied to the building material in a stereolithographic system. A fourth need exists for improved efficiency in exposing the building material in a stereolithographic system when exposure is controlled by a plurality of different vector types. A fifth need exists for simplified techniques for determining the maximum useful laser power for exposing a given set of vectors.
2. Other Related Patents and Applications
The patents, applications, and publications mentioned above and hereafter are all incorporated by reference herein as if set forth in full. Table 1 provides a listing of patents and applications co-owned by the assignee of the instant application. A brief description of subject matter found in each patent and application is included in the table to aid the reader in finding specific types of teachings. It is not intended that the incorporation of subject matter be limited to those topics specifically indicated, but instead the incorporation is to include all subject matter found in these applications and patents. The teachings in these incorporated references can be combined with the teachings of the instant application in many ways. For example, the references directed to various data manipulation techniques may be combined with the teachings herein to derive even more useful, modified object data that can be used to more accurately and/or efficiently form objects. As another example, the various apparatus configurations disclosed in these references may be used in conjunction with the novel features of the instant invention.
TABLE 1 Related Patents and Applications U.S. Pat. No. Issue Date Application No. Filing Date Inventor Subject 4,575,330 Hull Discloses fundamental elements of Mar 11, 1986 stereolithography. 06/638,905 Aug 8, 1984 4,999,143 Hull, et al. Discloses various removable support Mar 12, 1991 structures applicable to 07/182,801 stereolithography. Apr 18, 1988 5,058,988 Spence Discloses the application of beam Oct 22, 1991 profiling techniques useful in 07/268,816 stereolithography for determining Nov 8, 1988 cure depth and scanning velocity, etc. 5,059,021 Spence, et al. Discloses the utilization of drift Oct 22, 1991 correction techniques for eliminating 07/268,907 errors in beam positioning resulting Nov 8, 1988 from instabilities in the beam scanning system 5,076,974 Modrek, et al. Discloses techniques for post Dec 31, 1991 processing objects formed by 07/268,429 stereolithography. In particular Nov 8, 1988 exposure techniques are described that complete the solidification of the building material. Other post processing steps are also disclosed such as steps of filling in or sanding off surface discontinuities. 5,104,592 Hull Discloses various techniques for Apr 14, 1992 reducing distortion, and particularly 07/339,246 curl type distortion, in objects being Apr 17, 1989 formed by stereolithography. 5,123,734 Spence, et al. Discloses techniques for calibrating a Jun 23, 1992 scanning system. In particular tech- 07/268,837 niques for mapping from rotational Nov 8, 1988 mirror coordinates to planar target surface coordinates are disclosed 5,133,987 Spence, et al. Discloses the use of a stationary JuI 28, 1992 mirror located on an optical path 07/427,885 between the scanning mirrors and the Oct 27, 1989 target surface to fold the optical path in a stereolithography system. 5,141,680 Almquist, et al. Discloses various techniques for Aug 25, 1992 selectively dispensing a material 07/592,559 to build up three-dimensional objects. Oct 4, 1990 5,143,663 Leyden, et al. Discloses a combined stereo- Sep 1, 1992 lithography system for building 07/365,444 and cleaning objects. Jun 12, 1989 5,174,931 Almquist, et al. Discloses various doctor blade Dec 29, 1992 configurations for use in 07/515,479 forming coatings of medium adjacent Apr 27, 1990 to previously solidified laminae. 5,182,056 Spence, et al. Discloses the use of multiple Jan 26, 1993 wavelengths in the exposure of a 07/429,911 stereolithographic medium. Oct 27, 1989 5,182,715 Vorgitch, et al. Discloses various elements of a Jan 26, 1993 large stereolithographic system. 07/824,819 Jan 22, 1992 5,184,307 Hull, et al. Discloses a program called Slice and Feb 2, 1993 various techniques for converting 07/331,644 three-dimensional object data into Mar 31, 1989 data descriptive of cross-sections. Disclosed techniques include line width compensation techniques (erosion routines), and object sizing techniques. The application giving rise to this patent included a number of appendices that provide further details regarding stereolithography methods and systems. 5,192,469 Hull, et al. Discloses various techniques for Mar 9, 1993 forming three-dimensional object 07/606,802 from sheet material by selectively Oct 30, 1990 cutting out and adhering laminae. 5,209,878 Smalley, et al. Discloses various techniques for May 11, 1993 reducing surface discontinuities 07/605,979 between successive cross-sections Oct 30, 1990 resulting from a layer-by-layer building technique. Disclosed tech- niques include use of fill layers and meniscus smoothing. 5,234,636 Hull, et al. Discloses techniques for reducing Aug 10, 1993 surface discontinuities by 07/929,463 coating a formed object with a Aug 13, 1992 material, heating the material to cause it to become flowable, and allowing surface tension to smooth the coating over the object surface. 5,238,639 Vinson, et al. Discloses a technique for Aug 24, 1993 minimizing curl distortion by 07/939,549 balancing upward curl to Mar 31, 1992 downward curl. 5,256,340 Allison, et al. Discloses various build/exposure Oct 26, 1993 styles for forming objects 07/906,207 including various techniques for Jun 25, 1992 reducing object distortion. and Disclosed techniques include: 08/766,956 (1) building hollow, partially Dec 16, 1996 hollow, and solid objects, (2) achieving more uniform cure depth, (3) exposing layers as a series of separated tiles or bullets, (4) using alternate sequencing exposure patterns from layer to layer, (5) using staggered or offset vectors from layer to layer, and (6) using one or more over- lapping exposure patterns per layer. 5,321,622 Snead, et al. Discloses a computer program known Jun 14, 1994 as CSilce which is used to convert 07/606,191 three-dimensional object data into Oct 30, 1990 cross-sectional data. Disclosed techniques include the use of various Boolean operations in stereolithography. 5,597,520 Smalley, et al. Discloses various exposure Jan 28, 1997 techniques for enhancing object 08/233,027 formation accuracy. Disclosed Apr 25, 1994 techniques address formation of high and resolution objects from building 08/428,951 materials that have a Minimum Apr 25, 1995 Solidification Depth greater than one layer thickness and/or a Minimum Recoating Depth greater than the desired object resolution. 08/722,335 Thayer, et al. Discloses build and support styles Sep 27, 1996 for use in a Multi-Jet Modeling selective deposition modeling system. 5,943,235 Earl, et al Discloses data manipulation and Aug 24, 1999 system control techniques for use in a 08/722,326 Multi-Jet Modeling selective Sep 27, 1996 deposition modeling system. 5,902,537 Almquist, et al. Discloses various recoating May 11, 1999 techniques for use in stereo- 08/790,005 lithography. Disclosed techniques Jan 28, 1997 include 1) an ink jet dispensing device, 2) a fling recoater, 3) a vacuum applicator, 4) a stream recoater, 5) a counter rotating roller recoater, and 6) a technique for deriving sweep extents. 5,840,239 Partanen, et al. Discloses the application of solid- Nov 24, 1998 state lasers to stereolithography. 08/792,347 Discloses the use of a pulsed Jan 31, 1997 radiation source for solidifying layers of building material and in particular the ability to limit pulse firing locations to only selected target locations on a surface of the medium. 6,001,297 Partanen, et al. Discloses the stereolithographic Dec 14, 1999 formation of objects using a pulsed radiation source where pulsing occurs at selected positions on the surface of a building material. 6,084,980 Nguyen, et al. Discloses techniques for interpolating Jul 4, 2000 originally supplied cross-sectional 08/855,125 data descriptive of a three- May 13, 1997 dimensional object to produce modi- fied data descriptive of the three- dimensional object including data descriptive of intermediate regions between the originally supplied cross- sections of data. 5,945,058 Manners, et al. Discloses techniques for identifying Aug 31, 1999 features of partially formed objects. 08/854,950 Identifiable features include trapped May 13, 1997 volumes, effective trapped volumes, and solid features of a specified size. The identified regions can be used in automatically specifying recoating parameters and or exposure parameters. 5,902,538 Kruger, et al. Discloses simplified techniques for May 11, 1999 making high-resolution objects 08/920,428 utilizing low-resolution materials Aug 29, 1997 that are limited by their inability to reliably form coatings of a desired thickness due to a Minimum Recoating Depth (MRD) limitation. Data manipulation techniques define layers as primary or secondary. Recoating techniques are described which can be used when the thickness between consecutive layers is less than a leading edge bulge phenomena. 09/061,796 Wu, et al. Discloses use of frequency converted Apr 16, 1998 solid state lasers in stereolithography. 09/154,967 Nguyen, et al. Discloses techniques for Sep 17, 1998 stereolithographic recoating using a (now abandoned.) sweeping recoating device that pause and/or slows down over laminae that are being coated over. 09/484,984 Earl, et al. Entitled "Method and Apparatus for filed Jan 18, 2000 Forming Three-Dimensional Objects based on Using Line Width Compensation with Provisional Small Feature Retention." Discloses App. 60/116,281 techniques for forming objects while filed Jan 19, 1999 compensating for solidification width induced in a building material by a beam of prescribed stimulation. 09/246,504 Guertin, et al. Entitled "Method and Apparatus for file Feb 8, 1999 Stereolithographically Forming Three concurrently Dimensional Objects With Reduced herewith, Distortion."Discloses techniques for forming objects wherein a delay is made to occur between successive exposures of a selected region of a layer. 09/248,352 Manners, et al. Entitled Stereolithographic Method filed Feb 8, 1999 and Apparatus for Production of concurrently Three Dimensional Object Using herewith Multiple Beams of Different Diameters" Discloses stereo- lithographic techniques for forming objects using multiple sized beams including data manipulation techniques for determining which portions of lamina may be formed with a larger beam and which should be formed using a smaller beam. 6,103,176 Nguyen, et al. Entitled "Stereolithographic Method issued and Apparatus for Production of Aug 15, 2000, Three Dimensional Objects Using filed Feb 8, 1999 Recoating Parameters for Groups of concurrently Layers." Discloses improved herewith techniques for managing recoating parameters when forming objects using layer thicknesses smaller than a minimum recoating depth (MRD) and treating some non-consecutive layers as primary layers and treating intermediate layers there between as secondary layers. 09/246,416 Bishop, et al. Entitled "Rapid Prototyping filed Feb 8, 1999 Apparatus with Enhanced Thermal concurrently and Vibrational Stability for herewith Production of Three Dimensional Objects." Discloses an improved Stereolithographic apparatus structure for isolating vibration and/or extraneous heat producing components from other thermal and vibration sensitive components. 09/247,113 Chari, et al Entitled "Stereolithographic Method filed Feb 8, 1999 and Apparatus for production of concurrently Three Dimensional Objects with herewith Enhanced thermal Control of the Build environment. Discloses improved stereolithographic tech- niques for maintaining build chamber temperature at a desired level. The techniques include varying heat production based on the difference between a detected temperature and the desired temperature. 09,247,119 Kulkarni, et al. Entitled "Stereolithographic Method filed Feb 8, 1999 and Apparatus for Production of concurrently Three Dimensional Objects Including herewith Simplified Build Preparation." Discloses techniques for forming objects using a simplified data preparation process. Selection of the various parameter styles needed to form an object is reduced to answering several questions from lists of possible choices.
The following two books are also incorporated by reference herein as if set forth in full: (1) Rapid Prototyping and Manufacturing: Fundamentals of Stereolithography, by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1992; and (2) Stereolithography and other RP&M Technologies: from Rapid Prototyping to Rapid Tooling; by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1996.